This invention relates broadly to buckle-type sheet folding machines and more particularly to an infinitely variable power drive therefor.
A buckle-type folding machine normally comprises a series of rollers and fold-pan assemblies. A sheet of paper to be folded is inserted between two rotating rollers of a first roller set and is driven by these two rollers into a fold pan of a fold-pan assembly. A forward edge of the sheet eventually strikes a paper stop in the fold-pan; however, the two rollers continue to feed the sheet forward. Thus, the sheet buckles and the bulge of this buckle eventually extends between two rollers of a second roller set. These rollers fold the sheet at the bulge and feed this folded edge into a second fold pan of a second fold pan assembly. Upon striking a second paper stop there is a new buckle in the sheet and this buckle is, in turn, inserted between two rollers of a third roller set. This process continues until the sheet is folded a desired number of times.
After passing through a first buckle fold section, a sheet having parallel folds may then be conveyed to a second fold section at a right angle to the first in order to make folds perpendicular to the first folds. The sheets may then be fed to a third fold section and so on, each section being positioned at a right angle to the next preceding section. Alternatively, two or more sections may be arranged in tandem rather than at right angles.
The speed of each section of a multisection fold machine will vary according to the sheet length and the position and number of folds made in that section. To provide for this variable speed, two approaches have been used in prior buckle folders having independent sections. According to one approach, each section has its own independent drive motor. These machines have the disadvantage that each independent section of the folder must be adjusted for speed independently. Thus, when the overall speed of the system is changed, an operator must move to each section and reset that section's speed.
It is an object of this invention therefore to provide a variable speed drive to a multisection buckle fold feeder whereby the speed of the entire system may be varied after set-up by a single adjustment.
According to another prior-art approach, a drive motor is provided at the first fold section and a drive connection is made to each section through some mechanical variable speed device such as a varisheave. Mechanical variable speed devices, however, suffer from the disadvantage of being limited to speed variations of about four to one. Thus, where the folder is set up at a minimum speed of 1500 inches per minute, the maximum production speed of the machine would only be 6000 inches per minute; and, moreover, such devices also suffer from high power loss.
It is another object of this invention, therefore, to provide a variable speed drive to a buckle folder having a greater speed range, both overall and between sections, than has been possible with prior machines.